Recovery of fine colloidal material from solutions where the solid particles are very small and/or where the solids content is low has proven to be difficult, especially when the solution has a very low pH (<1.5), like strong acid leach stage thickener overflow. The very low pH is achieved by high acid content, which also means that the solution has high viscosity.
In these conditions, typical separation methods are too expensive or the particle size is too small for filtration and/or precipitation, for example.
Different filtration methods have been tested to recover the fine colloidal material from strong acid leach stage thickener overflow, however without any luck. Either filters have not been able to remove the fines, or the filters elements have been totally clogged, or the filter itself could not just handle the very difficult environment of the process without disintegrating.
One of the disadvantages associated therein is that valuable substances are lost, which leads to reduced extraction yields of the desired substances and increased operating costs.